This invention relates generally to traction devices for vehicle wheels, e.g. for automobiles, jeeps, vans, trucks, plows, three wheel vehicles, two wheel vehicles, etc. More specifically, this invention relates to an anti-slip device which is attached to a vehicle wheel in order to enhance wheel to ground contact in inclement weather conditions, e.g. snow, ice, etc.
Under certain whether conditions, normal vehicle wheels do not provide sufficient ground engagement, such normal vehicle wheels usually being constructed from a resilient material, such as rubber, having treads therein and sometimes having metal studs, etc., to enhance friction in certain environments.
A. The Related Art and Problems Therein
In the past, it has been known to apply chains to vehicle wheels in order to enhance friction contact on slippery roads, such as on ice or snow. However, such chains can be difficult to place upon a wheel, can be somewhat unstable upon the wheel, and can rattle, etc., during use causing noise and/or possible damage due to linkage wear, etc. In addition, such chains are usually somewhat difficult to place upon the wheel--e.g. requiring the wheel to be lifted or to be rotated over the chains.
There have also been a number of anti-skid devices which are attachable to a vehicle wheel and which include a number of cleat-like members crossing the tire tread of the wheel. Examples of such anti-skid devices include: (1) U.S. Pat. No. 4,862,936, (2) U.S. Pat. No. 4,089,359, (3) U.S. Pat. No. 3,016,079, (4) U.S. Pat. No. 2,873,783, and (5) U.S. Pat. No. 2,767,761.
However, the present inventor has discovered that the existing devices have a variety of problems. A number of such problems with these existing devices can be seen with respect to U.S. Pat. No. 4,089,359, number (2) above, which shows an anti-skid device having a number of cleats 14 which are biased inwardly via a spring.
First, in this latter type of device, the sliding motion of the cleats 14 is generally perpendicular to the vertical load from the wheel, e.g. generally axially into the cylindrical member 35. Accordingly, the cleats must be maintained straight in order to enable proper axial movement within the guides. However, the sliding motion of the cleats takes place generally perpendicular to a generally horizontal load imparted to the cleats from the wheel's rotational movement, or moment, against the ground, e.g. snow, therebelow. In addition, because the cleats move along a single `axis`, any forces acting upon the cleats which are not directly along that axis could cause a potentially damaging moment force. As a result, a significant warpage and/or deformation can occur in the cleats and/or the guides. This can easily hamper the sliding motion and can even cause sliding within the guides to become impossible. In order to avoid such deformation, it becomes important to make this device sufficiently rigid to avoid such deformation. However, when the device is made heavier, to enhance rigidity, the device also becomes difficult, or impossible, to handle for manual installation.
Second, the present inventor has discovered that the attachment pressure of the cleats to the tread surface of the wheel should preferably be maintained sufficient against the wheel, especially when the claw is located in the zone of contact between the wheel and the ground surface in which the wheel is usually compressed (see, e.g., FIG. 2). The distance from the surface of the wheel to its center axis usually decreases significantly in this zone. However, where individual springs are arranged to axially compress, such as in U.S. Pat. No. 4,089,359 (No. (2) above) (see also, U.S. Pat. Nos. (a) 2,477,051, (b) 2,601,882, (c) 3,016,079, (d) 3,996,984 and (e) 4,089,359), the pressure exerted by the individual springs falls sharply as the cleats move inward. Accordingly, the pressure exerted can decrease too great, so as to potentially make the device ineffectual.
Third, many of the devices known can not be used universally. That is, the devices are limited to applicability to only certain wheels having specified size, type, construction, or the like. As illustrated in, for example, the above U.S. Patents (a)-(e), some devices are attached to the wheel's hub, or hubcap. However, as should be apparent, there is a great variety of hub cap styles, etc., rendering such devices rather limited in universal applicability.